JP4470053B2 - Method for producing lithium cobalt composite oxide - Google Patents

Description

【Technical field】
[0001]
  The present invention relates to lithium cobalt composite oxidation for lithium secondary batteries.ThingManufacturing methodTo the lawRelated.
[Background]
[0002]
  In recent years, as devices become portable and cordless, expectations for non-aqueous electrolyte secondary batteries that are small, lightweight, and have high energy density are increasing. LiCoO as an active material for non-aqueous electrolyte secondary batteries₂LiNiO₂, LiNi_0.8Co_0.2O₂, LiMn₂O₄LiMnO₂There are known composite oxides of lithium and transition metals.
  Among these, lithium cobalt composite oxide (LiCoO₂) Is used as a positive electrode active material, and lithium secondary batteries using carbon such as lithium alloy, graphite, and carbon fiber as negative electrodes are widely used as batteries having high energy density because a high voltage of 4V is obtained. Yes.
  However, the conventional lithium secondary battery has problems such as deterioration of cycle characteristics in which the battery discharge capacity gradually decreases due to repeated charge / discharge cycles, or insufficient safety. Further, higher density is also required in terms of volume capacity density.
[0003]
  In order to improve these battery characteristics, Japanese Patent Laid-Open No. 10-1316 discloses cobalt hydroxide or oxyhydroxide whose cobalt valence is trivalent for the purpose of improving the cycle characteristics and the like of the lithium secondary battery. LiCoO obtained by dispersing cobalt in an aqueous lithium hydroxide solution and then heat-treating it.₂It has been proposed to use as an active material.
  In addition, Japanese Patent Laid-Open Nos. 10-279315 and 11-49519 disclose dicobalt trioxide (Co) in which the valence of cobalt is trivalent.₃O₂LiCoO obtained by mixing cobalt oxyhydroxide or the like with lithium oxide or the like and firing the mixture at 250 to 1000 ° C.₂It has been proposed that a lithium secondary battery having a high capacity and good cycle characteristics is used as an active material.
[0004]
  JP-A-10-31805 discloses a hexagonal system in which the c-axis length of the lattice constant is not more than 14.051 mm and the crystallite diameter in the (110) direction of the crystallite is 45 to 100 nm. LiCoO₂It has been proposed to improve the cycle characteristics of a lithium secondary battery by using as a positive electrode active material.
  Japanese Patent Publication No. 7-32017 discloses LiCoO in which 5-35% of Co atoms are substituted with W, Mn, Ta, Ti, or Nb.₂Has been proposed to improve the cycle characteristics of lithium secondary batteries. JP-A-6-64928 proposes improvement of self-discharge characteristics of a lithium secondary battery by using a Ti-containing lithium cobalt composite oxide as a positive electrode active material by a synthesis method using a molten salt. ing.
  However, in lithium secondary batteries using lithium-cobalt composite oxide as the positive electrode active material, conventionally, cycle characteristics, initial weight capacity density, volume capacity density, safety and low temperature operability, and a manufacturing method that facilitates mass production, etc. It is not yet known what will satisfy all of them.
[Problems to be solved by the invention]
[0005]
  The present invention has a large electric capacity, good discharge characteristics at low temperature, excellent charge / discharge cycle durability, initial weight capacity density, volume capacity density, and lithium cobalt composite oxidation for lithium secondary batteries having high safety.ThingManufacturing methodThe lawThe purpose is to provide.
[Means for Solving the Invention]
[0006]
  When the lithium cobalt composite oxide having a specific composition and crystal structure is used for a positive electrode of a lithium secondary battery, the present inventors have excellent battery characteristics, and in particular, a lithium cobalt composite obtained by a specific manufacturing method. It has been found that an oxide is excellent in mass productivity, and a lithium secondary battery in which the composite oxide is used as a positive electrode active material has particularly excellent cycle characteristics, and is excellent in safety and low-temperature operability.
  The present invention relates to the formula LiCo_1-XM_XO₂Where x is0.0005≦ x ≦ 0.02, M is at least one selected from the group of Ta, Ti, Nb, Zr and Hf, and 2θ = 66.5 ± 1 measured by X-ray diffraction using CuKα as a radiation source The (110) plane diffraction peak half-value width of0.100~0.165°RuHexagonal lithium cobalt oxide for lithium secondary batteryWith an average particle diameter of 1 to 20 μm and a specific surface area of 2 to 200 m ² / G cobalt oxyhydroxide powder, an average particle size of 1 to 50 μm and a specific surface area of 0.1 to 10 m ² / G lithium carbonate powder, an average particle size of 10 μm or less and a specific surface area of 1 to 100 m ² / G of metal element M oxide powder is dry-mixed, and the mixture is fired at 850 to 1000 ° C. in an oxygen-containing atmosphere to produce a hexagonal lithium cobalt composite oxide for a lithium secondary battery MethodI will provide a.
BEST MODE FOR CARRYING OUT THE INVENTION
[0007]
  UpIn the formula of the lithium cobalt composite oxide, if x is larger than 0.02, the initial electric capacity is lowered, which is not preferable.. MaFurthermore, from the effect of improving cycle durability and low temperature operability, x is 0.0005 ≦ x ≦ 0.02.AndParticularly preferably, 0.001 ≦ x ≦ 0.01, and more preferably 0.002 ≦ x ≦ 0.007.
  In addition, the (110) plane diffraction peak half width of 2θ = 66.5 ± 1 ° measured by X-ray diffraction using CuKα of the lithium cobalt composite oxide as a radiation source is in a specific direction of the lithium cobalt composite oxide. Reflecting the crystallite diameter, it was found that the larger the peak half-width, the smaller the crystallite diameter. In the present invention, the peak half-value width means a peak width at a half of the peak height.
[0008]
  The half width of the (110) plane diffraction peak of the lithium cobalt composite oxide of the present invention is0.100~0.165°. This half-width is0.100If it is less than 0 °, the charge / discharge cycle durability, initial electric capacity, average discharge voltage, or safety of the battery used as the positive electrode active material decreases, which is not preferable. In addition, the full width at half maximum is0.165Exceeding ° is not preferable because the initial electrical capacity and safety of the battery will decrease..
  Furthermore, the present invention has an average particle size of 1 to 20 μm and a specific surface area of 2 to 200 m.²/ G cobalt oxyhydroxide powder, an average particle size of 1 to 50 μm and a specific surface area of 0.1 to 10 m²/ G lithium carbonate powder and,flatAverage particle size of 10 μm or less and specific surface area of 1 to 200 m²Hexagonal lithium for a lithium secondary battery, which is dry-mixed with an oxide powder of a metal element M / g and calcined in an oxygen-containing atmosphere at 850 to 1000 ° C., preferably for 4 to 30 hours A method for producing a cobalt composite oxide is provided.
[0009]
  In the present invention, the average particle diameter means the weight average particle diameter. In the present invention, the average particle size is a particle size at which the cumulative curve of mass becomes 50% in a cumulative curve obtained by obtaining a particle size distribution on a mass basis and setting the total mass to 100%. This is also referred to as a mass-based cumulative 50% diameter (for example, Chemical Engineering Handbook “Revised 5th Edition” (edited by the Chemical Engineering Society) p220-221, Kirk-Othmer, “Encyclopedia of Chemical Technology”, 3rd. Edition, vol. 21, 106-113 (Wiley-Interscience) The particle size is measured by sufficiently dispersing in a medium such as water by ultrasonic treatment or the like (for example, using Microtrac HRAX-100 manufactured by Nikkiso Co., Ltd.). Is done.
[0010]
  The production method of the present invention uses the cobalt oxyhydroxide having the specific properties described above as a cobalt raw material.TheIf the average particle size of the cobalt oxyhydroxide is less than 1 μm, the safety of the battery is lowered or the packing density of the electrode layer is lowered. As a result, the electric capacity per volume is not preferred. Further, if the average particle size of the cobalt oxyhydroxide exceeds 20 μm, the discharge characteristics at a large current in the battery deteriorate, which is not preferable. The preferable average particle diameter of cobalt oxyhydroxide is 4-15 micrometers.
[0011]
  The cobalt oxyhydroxide may be produced in a water-containing state, but in such a case, it is difficult to measure the specific surface area. Therefore, in the present invention, the specific surface area of the water-containing cobalt oxyhydroxide is the water content of the cobalt oxyhydroxide. It means the specific surface area of a powder obtained by drying and dehydrating a product at 120 ° C. for 16 hours. In addition, when using hydrous cobalt oxyhydroxide, it is preferable to use the powder after drying, for example, it is preferable to use after drying at 120 degreeC for 16 hours. In the present invention, the specific surface area of cobalt oxyhydroxide is 2 m.²If it is less than / g, the discharge capacity at a large current decreases, which is not preferable. The specific surface area of cobalt oxyhydroxide is 200m.²If it exceeds / g, the packing density of the positive electrode layer is lowered, and as a result, the electric capacity per volume is lowered. The preferred specific surface area of cobalt oxyhydroxide is 20-100m²/ G.
[0012]
  The production method of the present invention uses lithium carbonate having specific properties as a lithium raw material.TheWhen the average particle size of lithium carbonate is less than 1 μm, the bulk density of the powder is lowered, and the productivity during mass production is lowered, which is not preferable. Moreover, when the average particle diameter of lithium carbonate exceeds 100 μm, the initial electric capacity is lowered, which is not preferable. The particularly preferable average particle diameter of lithium carbonate is 5 to 30 μm. The specific surface area of lithium carbonate is 0.1m²If it is less than / g, the initial discharge capacity per unit weight is lowered, which is not preferable. The specific surface area of lithium carbonate is 10m²If it exceeds / g, the packing density of the positive electrode layer is lowered, and as a result, the electric capacity per volume is lowered. The particularly preferred specific surface area of lithium carbonate is 0.3 to 3 m.²/ G.
[0013]
  In the method for producing a lithium cobalt composite oxide of the present invention,,originalMetal oxides with specific properties are used as metal oxides containing element MTheThe metal oxide containing the element M is titanium oxide TiO when M is titanium (Ti).₂Is preferably exemplified. Titanium oxide includes anatase type, rutile type, and the like, and it is particularly preferable to use anatase type because battery characteristics are good. Nb when M is niobium (Nb)₂O₅Is preferably exemplified. Ta when M is tantalum (Ta)₂O₅Is preferably exemplified. When M is zirconium (Zr), zirconium oxide ZrO₂Is preferably exemplified. HfO when M is hafnium (Hf)₂Is preferably exemplified.
[0014]
  If the average particle diameter of the metal oxide containing the element M exceeds 10 μm, the distribution of the element M in the lithium cobalt composite oxide particles becomes non-uniform, resulting in a decrease in the effect of adding the element M on the battery performance. . A preferable average particle diameter of the oxide composed of the element M is 1 μm or less, and particularly preferably 0.3 μm or less.
[0015]
  Specific surface area of metal oxide containing element M is 1 m²If it is less than / g, the reactivity decreases, and as a result, the effect of adding the element M on the battery performance decreases, which is not preferable. The specific surface area of the metal oxide containing the element M is 100 m.²Exceeding / g is not preferable because the element M is uniformly incorporated in the crystal lattice, and as a result, the effect of adding the element M on the battery performance decreases. The preferable specific surface area of the oxide containing the element M is 2 to 20 m.²/ G.
[0016]
  The lithium cobalt composite oxide of the present invention includes a cobalt oxyhydroxide powder, a lithium carbonate powder, and an oxide powder containing the element M.DryIt is preferable to obtain by baking in an oxygen-containing atmosphere at 850 to 1000 ° C., preferably for 4 to 30 hours, after the formula mixing. Wet mixing is not preferable because of low productivity. If the firing temperature is less than 850 ° C., the charge / discharge cycle durability decreases, which is not preferable. On the other hand, when the firing temperature exceeds 1000 ° C., the initial electric capacity is lowered, which is not preferable. Especially preferably, it is 870-960 degreeC, More preferably, it is 880-920 degreeC. A firing time of less than 4 hours is not preferable because the firing state becomes non-uniform during mass production and the characteristics tend to vary. If it is 30 hours or longer, productivity is lowered, which is not preferable. Particularly preferably, a firing time of 8 to 20 hours is employed.
[0017]
  The mixture is preferably fired under an oxygen stream. The oxygen concentration in the airflow is preferably 10 to 100% by volume, particularly preferably 19 to 50% by volume. If the oxygen concentration is low, the battery performance deteriorates, which is not preferable.
[0018]
  A lithium secondary battery using a positive electrode obtained by the manufacturing method of the present invention and using a lithium cobalt composite oxide having a specific value of a diffraction peak half-width of a specific (110) plane as an active material has an initial capacitance. While maintaining it, it is superior in conventional low temperature operability and charge / discharge cycle durability.
[0019]
  Of the present inventionObtained by manufacturing methodAmong lithium cobalt composite oxides, the filling press density of the lithium cobalt composite oxide is 2.90 to 3.35 g / cm.³Is preferable because the capacity density per unit volume in the electrode layer of the positive electrode can be increased. In the present invention, the filling press density means that the lithium cobalt composite oxide powder is 0.3 t / cm.²This means the apparent density of the press-molded product when pressed with a load of.
[0020]
  Filling press density is 2.90 g / cm³If it is less than the lower limit, the density of the positive electrode layer is decreased, and as a result, the capacity per volume is decreased. Filling press density is 3.35 g / cm³Exceeding this is not preferable because the capacity development at a high current density of the battery is lowered. The filling press density of the lithium cobalt composite oxide is 3.05 to 3.25 g / cm.³Is particularly preferred.
[0021]
  Of the present inventionUsing lithium cobalt composite oxide obtained by the manufacturing methodIn the lithium secondary battery, the present inventionObtained by manufacturing methodAfter applying a dispersion liquid comprising a slurry or a kneaded material containing a lithium cobalt composite oxide powder, a conductive material, a binder, and a solvent or dispersion medium of the binder to an aluminum foil, a positive electrode current collector such as a stainless steel foil, etc. It is preferable that the positive electrode is dried and supported. As the conductive material, carbon-based conductive materials such as acetylene black, graphite, and Ketchen black are preferably used. As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide, carboxymethyl cellulose, acrylic resin, or the like is preferably used. For the separator, porous polyethylene, porous polypropylene film or the like is preferably used.
[0022]
  Of the present inventionUsing lithium cobalt composite oxide obtained by the manufacturing methodIn the lithium secondary battery, a carbonate is preferable as the solvent of the electrolyte solution. The carbonate ester can be either cyclic or chain. Examples of cyclic carbonates include propylene carbonate and ethylene carbonate (EC). Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate (DEC), ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate and the like.
[0023]
  Of the present inventionUsing lithium cobalt composite oxide obtained by the manufacturing methodIn the lithium secondary battery, the carbonate ester can be used alone or in admixture of two or more. Moreover, you may mix with another solvent. Moreover, depending on the material of the negative electrode active material, when a chain carbonate ester and a cyclic carbonate ester are used in combination, discharge characteristics, cycle durability, and charge / discharge efficiency may be improved.
  In addition, vinylidene fluoride-hexafluoropropylene copolymer (for example, product name: Kyner manufactured by Atchem Co.), vinylidene fluoride-perfluoropropyl vinyl ether copolymer disclosed in JP-A-10-294131 is used in these organic solvents. It is good also as a gel polymer electrolyte by adding the following solute.
[0024]
  The solute of the electrolyte solution or polymer electrolyte is ClO.₄-, CF₃SO₃-, BF₄-, PF₆-, AsF₆-, SbF₆-, CF₃CO₂-, (CF₃SO₂)₂It is preferable to use at least one lithium salt having N- or the like as an anion. In the above electrolyte solution or polymer electrolyte, an electrolyte composed of a lithium salt is preferably added to the solvent or the solvent-containing polymer at a concentration of 0.2 to 2.0 mol / l (liter). If it deviates from this range, the ionic conductivity is lowered and the electrical conductivity of the electrolyte is lowered. More preferably, 0.5 to 1.5 mol / l is selected.
[0025]
  Of the present inventionUsing lithium cobalt composite oxide obtained by the manufacturing methodIn a lithium secondary battery using a positive electrode active material, a material capable of inserting and extracting lithium ions is used for the negative electrode active material. The material for forming this negative electrode active material is not particularly limited, but for example, lithium metal, lithium alloy, carbon material, periodic table 14, oxide mainly composed of group 15 metal, carbon compound, silicon carbide compound, silicon oxide compound, Examples thereof include titanium sulfide and boron carbide compounds. As the carbon material, those obtained by pyrolyzing organic substances under various pyrolysis conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, scale-like graphite, or the like can be used. As the oxide, a compound mainly composed of tin oxide can be used. As the negative electrode current collector, a copper foil, a nickel foil or the like is used.
[0026]
  The present inventionLithium cobalt composite oxide obtained by the manufacturing method ofUse positive electrode active materialbatteryAs in the case of the positive electrode, the negative electrode in is preferably obtained by kneading the negative electrode active material with an organic solvent to form a slurry, applying the slurry to a metal foil current collector, drying, and pressing.
  Of the present inventionUsing lithium cobalt composite oxide obtained by the manufacturing methodThere are no particular restrictions on the shape of the lithium secondary battery. A sheet shape (so-called film shape), a folded shape, a wound-type bottomed cylindrical shape, a button shape, or the like is selected depending on the application.
【Example】
[0027]
  The present invention will be described more specifically with reference to the following examples. However, the present invention should not be construed as being limited to these examples. In addition, the following examples 1 to example7Are examples of the present invention, examples8-Example 16 is a comparative example.
[0028]
[Example 1]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder, an average particle size of 0.22 μm and a specific surface area of 9 m²/ G of anatase-type titanium dioxide powder. Mixing ratio is LiCo after firing_0.998Ti_0.002O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  About the powder after baking (positive electrode active material powder), an X-ray diffraction spectrum was obtained using a RINT 2100 type X-ray diffractometer manufactured by Rigaku Corporation. In this powder X-ray diffraction using CuKα ray, a hexagonal diffraction peak was obtained. Further, the half value width of the diffraction peak of (110) plane around 2θ = 66.5 ± 1 ° was 0.121 °.
  This positive electrode active material powder was 0.3 t / cm.²And the filling press density was determined from the volume and weight of 3.20 g / cm.³Met.
[0029]
  LiCo thus obtained_0.998Ti_0.002O₂Powder, acetylene black, and polytetrafluoroethylene powder were mixed at a weight ratio of 80/16/4, kneaded while adding toluene, and dried to prepare a positive electrode plate having a thickness of 150 μm.
  Then, 20 μm thick aluminum foil is used as the positive electrode current collector, 25 μm thick porous polypropylene is used as the separator, 500 μm thick metal lithium foil is used as the negative electrode, and nickel foil 20 μm is used as the negative electrode current collector. 1M LiPF is used as the electrolyte.₆Two stainless steel simple sealed cell batteries were assembled in an argon glove box using / EC + DEC (1: 1).
[0030]
  For these two batteries, first, the battery was charged at a load current of 75 mA per 1 g of the positive electrode active material at 25 ° C. to 4.3 V, and discharged to 2.5 V at a load current of 75 mA per 1 g of the positive electrode active material. The capacity was determined. About one battery, the charge / discharge cycle test was further performed 40 times. The other battery was charged at 25 ° C., cooled to −10 ° C., discharged to 2.5 V at a load current of 75 mA per 1 g of the positive electrode active material, and the initial discharge capacity at −10 ° C. was obtained. The capacity expression rate at −10 ° C. when the initial electric capacity at 25 ° C. was taken as 100% was determined.
  The initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 149 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 95.3%. Moreover, the capacity | capacitance expression rate in -10 degreeC was 70%.
[0031]
[Example 2]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder, an average particle size of 0.15 μm and a specific surface area of 5.3 m²/ G niobium oxide Nb₂O₅The powder was mixed. Mixing ratio is LiCo after firing_0.998Nb_0.002O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.115 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.23 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.998Nb_0.002O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 148 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 95. 0.0%. Moreover, the capacity | capacitance expression rate in -10 degreeC was 73%.
[0032]
[Example 3]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder, an average particle size of 0.23 μm and a specific surface area of 9.8 m²/ G tantalum oxide Ta₂O₅The powder was mixed. Mixing ratio is LiCo after firing_0.998Ta_0.002O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.115 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.19 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.998Ta_0.002O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 148 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 96. It was 1%. Moreover, the capacity | capacitance expression rate in -10 degreeC was 75%.
[0033]
[Example 4]
  Average particle size 8μm and specific surface area 40m²/ G cobalt oxyhydroxide powder, average particle size 22 μm and specific surface area 0.64 m²/ G lithium carbonate powder, an average particle size of 0.17 μm and a specific surface area of 35 m²/ G of anatase-type titanium dioxide powder. Mixing ratio is LiCo after firing_0.994Ti_0.006O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were calcined at 890 ° C. for 15 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 19% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.127 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.11 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.994Ti_0.006O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 149 mAh / g, and the capacity retention ratio after 40 charge / discharge cycles was 95. 0.7%. The capacity expression rate at −10 ° C. was 72%.
[0034]
[Example 5]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder, an average particle size of 8.1 μm and a specific surface area of 15 m²/ G zirconium oxide (ZrO₂) The powder was mixed. Mixing ratio is LiCo after firing_0.998Zr_0.002O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  When the fired powder (positive electrode active material powder) was measured in the same manner as in Example 1, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.117 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.19 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.998Zr_0.002O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 148 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 95. 8%. The capacity expression rate at −10 ° C. was 68%.
[0035]
[Example 6]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder, an average particle size of 0.4 μm and a specific surface area of 7.2 m²/ G hafnium oxide (HfO₂) The powder was mixed. Mixing ratio is LiCo after firing_0.998Hf_0.002O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  When the fired powder (positive electrode active material powder) was measured in the same manner as in Example 1, the half value width of the diffraction peak of the (110) plane near 2θ = 66.5 ± 1 ° was 0.119 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.18 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.998Hf_0.002O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 2.5 to 4.3 V at 25 ° C. was 149 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 96. 0.0%. Moreover, the capacity | capacitance expression rate in -10 degreeC was 70%.
[0036]
[Example 7]
  Average particle size 8μm and specific surface area 40m²/ G cobalt oxyhydroxide powder, average particle size 22 μm and specific surface area 0.64 m²/ G lithium carbonate powder, an average particle size of 8.1 μm and a specific surface area of 16 m²/ G of zirconium oxide powder was mixed. Mixing ratio is LiCo after firing_0.994Zr_0.006O₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were calcined at 890 ° C. for 15 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 19% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.128 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.10 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.994Zr_0.006O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 148 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 95. 7%. The capacity expression rate at −10 ° C. was 72%.
[0037]
[Example 8]
  Average particle size 10μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder was mixed. Mixing ratio is LiCoO after firing₂It mix | blended so that it might become. After these three kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak of the (110) plane near 2θ = 66.5 ± 1 ° was 0.098 °.
When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.10 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  The two batteries were measured in the same manner as in Example 1. As a result, the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 149 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 94. It was 8%. Moreover, the capacity | capacitance expression rate in -10 degreeC was 54%.
[0038]
[Example 9]
  Average particle size 15μm and specific surface area 60m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder was mixed. Mixing ratio is LiCoO after firing₂It mix | blended so that it might become. After these two kinds of powders were dry-mixed, they were calcined at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.091 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.18 g / cm.³Met.
  LiCo from Example 1_0.998Ti_0.002O₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  One of the batteries was charged at a load current of 75 mA per gram of positive electrode active material at 25 ° C. to 4.3 V, and discharged to 2.5 V at a load current of 75 mA per gram of positive electrode active material. The discharge capacity was determined. Furthermore, about this battery, the charge / discharge cycle test was performed 30 times continuously. As a result, the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 149 mAh / g, and the capacity retention rate after 30 charge / discharge cycles was 96.3%.
[0039]
  The other battery has a positive electrode area of 1 cm.²Is charged at a constant current of 0.2 mA up to 4.3 V, disassembled in an argon glove box, and the charged positive electrode sheet is taken out. After washing the positive electrode sheet, it is punched into a diameter of 3 mm and sealed in an aluminum capsule together with EC. The temperature was increased at a rate of 5 ° C./min with a scanning differential calorimeter, and the heat generation start temperature was measured. As a result, the heat generation start temperature was 165 ° C.
[0040]
[Example 10]
  Average particle size 8μm and specific surface area 50m²/ G cobalt oxyhydroxide powder, average particle size 15μm and specific surface area 1.2m²/ G lithium carbonate powder was mixed. Mixing ratio is LiCoO after firing₂It mix | blended so that it might become. After these two kinds of powders were dry-mixed, they were baked at 910 ° C. for 12 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 28% by volume.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.095 °.
When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 3.01 g / cm.³Met.
[0041]
  LiCo from Example 1_0.998Ti_0.002O₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  For one of them, the initial electric capacity of the battery and the capacity after 30 cycles were determined in the same manner as in Example 9, and the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 148 mAh / g, 30 times. The capacity retention rate after the charge / discharge cycle was 97.0%.
  Moreover, when the reactivity with the electrolyte solution of the charged positive electrode active material was calculated | required about the other battery like Example 9, the heat_generation | fever start temperature was 169 degreeC.
[0042]
[Example 11]
  Average particle size 12μm and specific surface area 66m²/ G cobalt oxyhydroxide powder, average particle size 28 μm and specific surface area 0.43 m²/ G lithium carbonate powder was mixed. Mixing ratio is LiCoO after firing₂It mix | blended so that it might become. After these two kinds of powders were dry-mixed, they were baked at 890 ° C. for 18 hours in an atmosphere in which oxygen gas was added to air to make the oxygen concentration 19% by volume.
  When the fired powder (positive electrode active material powder) was measured in the same manner as in Example 1, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.083 °.
  The filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, and was found to be 3.12 g / cm.³Met.
[0043]
  LiCo from Example 1_0.998Ti_0.002O₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
For one of them, the initial electric capacity of the battery and the capacity after 30 cycles were determined in the same manner as in Example 9, and the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 148 mAh / g, 30 times. The capacity retention rate after the charge / discharge cycle was 95.3%.
  Moreover, when the reactivity with the electrolyte solution of the charged positive electrode active material was calculated | required about the other battery like Example 9, the heat_generation | fever start temperature was 173 degreeC.
[0044]
[Example 12]
  Instead of cobalt oxyhydroxide, average particle size 8μm, specific surface area 0.66m²/ G cobalt oxide (Co₃O₄) LiCoO as in Example 9 except that powder was used₂Was synthesized.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 9. As a result, the half value width of the diffraction peak of the (110) plane near 2θ = 66.5 ± 1 ° was 0.133 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 2.75 g / cm.³Met.
[0045]
  LiCoO of Example 9₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  For one of them, the initial electric capacity of the battery and the capacity after 30 cycles were determined in the same manner as in Example 9, and the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 148 mAh / g, 30 times. The capacity retention rate after the charge / discharge cycle was 96.4%.
  Moreover, when the reactivity with the electrolyte solution of the charged positive electrode active material was calculated | required about the other battery like Example 9, the heat_generation | fever start temperature was 155 degreeC.
[0046]
[Example 13]
  Average particle size 15μm and specific surface area 60m²/ G instead of cobalt oxyhydroxide powder, average particle size 30μm, specific surface area 7m²LiCoO in the same manner as in Example 9 except that the cobalt oxyhydroxide powder of / g was used.₂Was synthesized.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak of the (110) plane near 2θ = 66.5 ± 1 ° was 0.118 °.
  The filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, and was found to be 3.15 g / cm.³Met.
  LiCoO of Example 9₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  For one of them, the initial electric capacity of the battery and the capacity after 30 cycles were determined in the same manner as in Example 9, and the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 137 mAh / g, 30 times. The capacity retention rate after the charge / discharge cycle was 92.3%.
  Moreover, when the reactivity with the electrolyte solution of the charged positive electrode active material was calculated | required about the other battery like Example 9, the heat_generation | fever start temperature was 158 degreeC.
[0047]
[Example 14]
  In the same manner as in Example 9 except that the firing at 910 ° C. for 12 hours in Example 9 was changed to the firing at 780 ° C. for 12 hours, LiCoO₂Was synthesized.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.138 °.
  When the filling press density of this positive electrode active material powder was determined in the same manner as in Example 1, it was 2.98 g / cm.³Met.
[0048]
  LiCoO of Example 9₂LiCoO above instead of powder₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  For one of them, the initial electric capacity of the battery and the capacity after 30 cycles were determined in the same manner as in Example 9, and the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 147 mAh / g, 30 times. The capacity retention rate after the charge / discharge cycle was 96.5%.
  Moreover, when the reactivity with the electrolyte solution of the charged positive electrode active material was calculated | required about the other battery like Example 9, the heat_generation | fever start temperature was 156 degreeC.
[0049]
[Example 15]
  LiCo after sintering the mixing ratio of cobalt oxyhydroxide powder, lithium carbonate powder and anatase titanium dioxide powder_0.95Ti_0.05O₂LiCo was prepared in the same manner as in Example 1 except that it was blended so that_0.95Ti_0.05O₂Was synthesized.
  The powder after baking (positive electrode active material powder) was measured in the same manner as in Example 1. As a result, the half value width of the diffraction peak on the (110) plane near 2θ = 66.5 ± 1 ° was 0.188 °.
  LiCo from Example 1_0.998Ti_0.002O₂LiCo above instead of powder_0.95Ti_0.05O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
  When these two batteries were measured in the same manner as in Example 1, the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 141 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 93. It was 6%. The capacity expression rate at −10 ° C. was 68%.
[0050]
[Example 16]
  LiCo after sintering the mixing ratio of cobalt oxyhydroxide powder, lithium carbonate powder and zirconium oxide_0.95Zr_0.05O₂LiCo was prepared in the same manner as in Example 5 except that_0.95Zr_0.05O₂Was synthesized.
  When the fired powder (positive electrode active material powder) was measured in the same manner as in Example 5, the half value width of the diffraction peak of the (110) plane near 2θ = 66.5 ± 1 ° was 0.183 °.
  LiCo from Example 5_0.998Zr_0.002O₂LiCo above instead of powder_0.95Zr_0.05O₂Two stainless steel simple sealed cell batteries were assembled in the same manner as in Example 1 except that powder was used.
[0051]
  When these two batteries were measured in the same manner as in Example 5, the initial discharge capacity at 25 ° C. and 2.5 to 4.3 V was 140 mAh / g, and the capacity retention rate after 40 charge / discharge cycles was 93. It was 8%. The capacity expression rate at −10 ° C. was 68%.
【The invention's effect】
[0052]
  According to the present invention, a hexagon having a large electric capacity, good discharge characteristics at low temperatures, excellent charge / discharge cycle durability, and high safety as a positive electrode active material for a lithium secondary battery. A crystalline lithium cobalt composite oxide and an efficient and advantageous method for producing such a lithium cobalt composite oxide are provided.
[0053]
  Also, a positive electrode for a lithium secondary battery using a hexagonal lithium cobalt composite oxide as an active material, and electric capacity, discharge characteristics, charge / discharge cycle durability, capacity density, safety and low temperature operability using such a positive electrode A lithium secondary battery excellent in terms of the characteristics is provided.

Claims (10)

Represented by the formula LiCo _1-X M _X O ₂ , where x is 0.0005 ≦ x ≦ 0.02 and M is at least one selected from the group of Ta, Ti, Nb, Zr and Hf. and it is measured by X-ray diffraction as a radiation source a CuKα 2θ = 66.5 ± 1 ° of the (110) plane diffraction peak half width 0.100 ~ 0.165 ° der ruri lithium secondary battery A method for producing a hexagonal lithium-cobalt composite oxide, wherein the cobalt oxyhydroxide powder has an average particle diameter of 1 to 20 μm and a specific surface area of ² to 200 m ² / g, an average particle diameter of 1 to 50 μm and a specific surface area of 0. .1-10 m ² / g lithium carbonate powder and metal element M oxide powder having an average particle size of 10 μm or less and a specific surface area of 1-100 m ² / g are dry-mixed, and the mixture is mixed at 850 to 1000 ° C. Firing in an oxygen-containing atmosphere A method for producing a hexagonal lithium-cobalt composite oxide for a lithium secondary battery. The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to claim 1, wherein a filling press density of the hexagonal lithium cobalt composite oxide is 2.90 to 3.35 g / cm ³ . The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to claim 1 or 2, wherein the mixture is fired for 4 to 30 hours. The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to any one of claims 1 to 3, wherein the mixture is fired at 870 to 960 ° C. Said x is 0.002 <= x <= 0.007, The manufacturing method of the hexagonal system lithium cobalt complex oxide for lithium secondary batteries in any one of Claims 1-4. The specific surface area of the metal element M oxide is 2 to 20 m. ² The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to any one of claims 1 to 5. Metal element M oxide is TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , ZrO ₂ Or HfO ₂ The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to any one of claims 1 to 6. The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to any one of claims 1 to 7, wherein the average particle diameter of the cobalt oxyhydroxide powder is 4 to 15 µm. The average particle diameter of lithium carbonate powder is 5-30 micrometers, The manufacturing method of the hexagonal system lithium cobalt complex oxide for lithium secondary batteries in any one of Claims 1-8. The method for producing a hexagonal lithium cobalt composite oxide for a lithium secondary battery according to any one of claims 1 to 9, wherein the oxygen concentration in the oxygen-containing atmosphere is 10 to 100% by volume.